The secretary-general of the North Atlantic Treaty Organization (NATO) has expressed confidence that Donald Trump would live up to all US commitments to the military alliance.

“President-elect Donald Trump stated during the election campaign that he is a big fan of NATO,” Jens Stoltenberg said in Brussels on Tuesday.

“And I am certain that he will be a president… who will live up to all the commitments of the United States in the alliance, because a strong NATO is important for Europe but it’s also important for the United States,” he stressed.

The comments came just days after Stoltenberg warned Trump not to distance the US from NATO, saying the West is facing its greatest security challenge in a generation.

Trump’s surprise victory over heavily-favored Hillary Clinton last week rattled nerves in Europe after he called NATO an “obsolete” military alliance and raised doubts whether the US under his command would assist a NATO ally under attack.

During his bombastic campaign, the billionaire businessman also appeared to be conciliatory towards Russia, praising President Vladimir Putin as a much stronger leader than President Barack Obama.

Donald Trump (file photo by Reuters)

Asked about a telephone call between Trump and Putin on Monday in which they discussed ways to improve US-Russian relations, Stoltenberg denied this was cause for concern.

“First of all, I think it is a very normal thing that president-elect Donald Trump speaks to world leaders, including of course the leader of Russia,” he said.

“The message from NATO has been that we want dialogue with Russia … especially when tensions are high, especially when we face many different challenges, it is important.”

Stoltenberg’s upbeat tone appeared to be a departure from his stern warning in an article in British daily The Observer on Sunday, in which he wrote that “going it alone is not an option… this is no time to question the partnership between Europe and the United States.”

During a press conference at the White House on Monday, President Obama also reassured US allies that his Republican successor will be committed to NATO.

Obama said Trump “expressed a great interest in maintaining our core strategic relationships” when they met at the White House last week.

The US accounts for nearly 70 percent of the NATO budget and has long urged its European allies to step up their contributions, particularly in the face of what Washington calls the “Russian aggression” in Ukraine.